Imaging of Orbit

Imaging of Imaging of OrbitOrbit

Dr. Faisal M. Shembesh.Dr. Faisal M. Shembesh.

Computed X-ray TomographyComputed X-ray TomographyIndications:Indications: CT remains the technique of choice for investigation of suspected CT remains the technique of choice for investigation of suspected orbital disease. orbital disease. Cost. Cost. Accessibility.Accessibility.Speed. Speed. High tissue contrast within the orbit. High tissue contrast within the orbit.

Pain. Pain. Deformity.Deformity.Proptosis.Proptosis.Swelling. Swelling. restriction of eye movements. restriction of eye movements. visual loss. visual loss.

CT of the eye is generally less sensitive than either sonography CT of the eye is generally less sensitive than either sonography or MRI. However, it is the examination of choice for or MRI. However, it is the examination of choice for demonstrating possibly intraocular demonstrating possibly intraocular foreign bodiesforeign bodies when when plain-film localisation is inadequate plain-film localisation is inadequate & orbital trauma& orbital trauma ..

Although MRI has the obvious advantages in this context of not Although MRI has the obvious advantages in this context of not using using ionising radiationionising radiation and of being able to generate images in and of being able to generate images in

any planeany plane, it should be regarded as a , it should be regarded as a complement to CT. complement to CT.

The insensitivity of MRI to The insensitivity of MRI to calcification,calcification, which may vitiate which may vitiate diagnosis of drusen, choroidal osteoma, senile scleral plaques or diagnosis of drusen, choroidal osteoma, senile scleral plaques or even optic nerve sheath meningioma even optic nerve sheath meningioma

Chemical shift artefactsChemical shift artefacts, which can simulate a capsule or , which can simulate a capsule or

calcification.calcification.

The general contraindications to MRI, such as The general contraindications to MRI, such as Metallic foreign bodies. intracranial Metallic foreign bodies. intracranial

aneurysm clips, pacemakers, nerve stimulators, and magnetic ocular prostheses,aneurysm clips, pacemakers, nerve stimulators, and magnetic ocular prostheses, must be must be borne in mind. Nevertheless, there are a number of well-defined borne in mind. Nevertheless, there are a number of well-defined

situations in which MRI can usefully complement CT.situations in which MRI can usefully complement CT.

Magnetic Resonance ImagingMagnetic Resonance ImagingIndicationsIndications

Magnetic Resonance ImagingMagnetic Resonance Imaging

IndicationsIndications

Distinction of lesions arising from the Distinction of lesions arising from the optic nerveoptic nerve oror its its sheathsheath from those which from those which about the optic nerve,about the optic nerve, when when

this is not evident on CT, is of major importance, since this is not evident on CT, is of major importance, since the former are rarely an indication for surgery, whereas the former are rarely an indication for surgery, whereas in the latter group surgery can be curative. The coronal in the latter group surgery can be curative. The coronal

plane is usually the most informative in this contextplane is usually the most informative in this context..

Demonstration of Demonstration of signal changesignal change within a within a morphologically normal morphologically normal optic nerveoptic nerve may be of largely may be of largely

academic interest, since it should rarely affect academic interest, since it should rarely affect treatment. However, in inflammatory disease, the ability treatment. However, in inflammatory disease, the ability to show that the process involves the to show that the process involves the nerve sheathnerve sheath (as (as in, say, sarcoidosis) rather than the in, say, sarcoidosis) rather than the nerve itselfnerve itself (as in (as in

demyelinating retrobulbar neuritis), may orientate demyelinating retrobulbar neuritis), may orientate management.management.



Demonstration of intracranial changes indicative of a Demonstration of intracranial changes indicative of a more widespread central nervous system disease. more widespread central nervous system disease.

Perhaps the most obvious example is when Perhaps the most obvious example is when plaques of plaques of demyelinationdemyelination are shown in a patient with an optic are shown in a patient with an optic

neuropathy of unknown cause. neuropathy of unknown cause. Meningeal infiltration, Meningeal infiltration, suggestive of granulomatous diseasesuggestive of granulomatous disease or or neoplasia,neoplasia,

may also orientate the diagnostic process.may also orientate the diagnostic process.



Thin sections are usually required. Thin sections are usually required. Axial and coronalAxial and coronal images are usually most helpful. The latter are images are usually most helpful. The latter are

preferred for assessment of the optic nerve and its preferred for assessment of the optic nerve and its sheath. sheath. Fat suppressionFat suppression is helpful; STIR, FLAIR or fat- is helpful; STIR, FLAIR or fat-

suppressed spin-echo sequences may be obtained. Fat suppressed spin-echo sequences may be obtained. Fat suppression is essential when contrast-enhanced suppression is essential when contrast-enhanced

images are obtained.images are obtained.


TechniqueTechnique

Orbital AnatomyOrbital Anatomy

Each Each orbital recessorbital recess contains the contains the globeglobe, , nervesnerves (II, III, IV, V, and VI), (II, III, IV, V, and VI), musclesmuscles, , bloodblood vesselsvessels, , connective tissueconnective tissue, and most of the , and most of the

lacrimal apparatuslacrimal apparatus. The bony orbit is . The bony orbit is bordered by the periosteumbordered by the periosteum

Seven bones comprise Seven bones comprise the orbitthe orbit

Frontal, Maxillary, Ethmoid, Frontal, Maxillary, Ethmoid, Sphenoid, Lacrimal, Palatine, and Sphenoid, Lacrimal, Palatine, and

Zygoma bones.Zygoma bones.

Tenon's capsule (fascia bulbi) Tenon's capsule (fascia bulbi)

is a fibroelastic membrane that envelops the eyeball from is a fibroelastic membrane that envelops the eyeball from the optic nerve to the ciliary muscle. The inner surface of the optic nerve to the ciliary muscle. The inner surface of

Tenon's capsule is separated from the outer surface of Tenon's capsule is separated from the outer surface of the sclera by a potential space - the episcleral or Tenon's the sclera by a potential space - the episcleral or Tenon's

spacespace..

Four orbital spacesFour orbital spaces::

((11) ) intraconal intraconal ((central orbitalcentral orbital))..((22) ) extraconal extraconal ((peripheral orbitalperipheral orbital)). . ((33) ) Tenon's. Tenon's. ((44) ) subperiostealsubperiosteal.. potential spaces.

separated from the other spaces by the rectus muscles

useful for surgical planning and for differential diagnosis .

Intra-orbital fatty reticulum is divided intoIntra-orbital fatty reticulum is divided into (1) peripheral orbital fat (1) peripheral orbital fat outside the muscle cone, and its intermuscular membranesoutside the muscle cone, and its intermuscular membranes

(2) the central orbital fat (2) the central orbital fat

which is within the muscle conewhich is within the muscle cone Retro-orbital fat

Orbital Imaging Orbital Imaging AnatomyAnatomy

Orbital PathologyOrbital Pathology

Developmental Orbital CystsDevelopmental Orbital Cysts

The most frequent developmental orbital The most frequent developmental orbital cysts are cysts are the dermoid and epidermoid cyststhe dermoid and epidermoid cysts. . Both result from the inclusion of ectodermal Both result from the inclusion of ectodermal elements during closure of the neural tube.elements during closure of the neural tube.

Dermoid and epidermoid cysts favor the Dermoid and epidermoid cysts favor the upper portionupper portion and in particular superior and in particular superior temporal quadranttemporal quadrant rather than the lower rather than the lower quadrants of the orbit for their growth.quadrants of the orbit for their growth.

On CT.On CT. Dermoid cysts which contain fat Dermoid cysts which contain fat (well-differentiated teratomas) show fat (well-differentiated teratomas) show fat

density, fluid-fluid levels, and density, fluid-fluid levels, and infrequently, calcification.infrequently, calcification.

On (MRI). These cysts show long T1 On (MRI). These cysts show long T1 and long T2 characteristics The fat and long T2 characteristics The fat

component of dermoids show, short component of dermoids show, short T1 and T2 characteristicsT1 and T2 characteristics. .

Inflammatory Diseases of the OrbitInflammatory Diseases of the Orbit

Orbital infections account for about Orbital infections account for about 60%60% of primary of primary orbital diseaseorbital disease processes. The process may be processes. The process may be acute, subacute or chronic the majority of acute acute, subacute or chronic the majority of acute

inflammatory disorders are of inflammatory disorders are of sinus origin.sinus origin.

The classification of orbital infection includes five categories or stages of orbital involvement from sinusitis:

(1)(1) inflammatory edema. inflammatory edema. (2)(2) subperiosteal phlegmon and abscess. subperiosteal phlegmon and abscess. (3)(3) orbital cellulitis. orbital cellulitis. (4)(4) orbital abscess. orbital abscess. (5)(5) ophthalmic vein and cavernous sinus thrombosisophthalmic vein and cavernous sinus thrombosis. .

MRI MRI remains the study of choice for intracranial remains the study of choice for intracranial complications of inflammatory conditions of the orbit and complications of inflammatory conditions of the orbit and

sinonasal cavitysinonasal cavity

Acute, Subacute and Chronic Idiopathic Acute, Subacute and Chronic Idiopathic Orbital Inflammatory DisordersOrbital Inflammatory Disorders

Idiopathic inflammatory orbital syndromes are Idiopathic inflammatory orbital syndromes are usually referred to as orbital "pseudotumors", a usually referred to as orbital "pseudotumors", a

clinically and histologically confusing category of clinically and histologically confusing category of lesions.lesions.

Pseudotumors may be classified as: (1) acute and subacute anterior idiopathic orbital inflammations. (2) acute and subacute idiopathic diffuse orbital inflammations.(3) acute and subacute idiopathic myositic orbital inflammations. (4) acute and subacute idiopathic apical orbital inflammations. (5) idiopathic dacryoadenitis. (6) idiopathic optic perineuritis. (7) posterior scleritis and tenon fasciitis.

CT and MRI findings include moderate to marked contrast CT and MRI findings include moderate to marked contrast enhancement of an infiltrative process involving the retrobulbar fat, enhancement of an infiltrative process involving the retrobulbar fat,

muscles, optic nerve, lacrimal gland, and tenon's capsule.muscles, optic nerve, lacrimal gland, and tenon's capsule.

Painful OphthalmoplegiaPainful Ophthalmoplegia

Painful external ophthalmoplegia, or Tolosa-Hunt Painful external ophthalmoplegia, or Tolosa-Hunt syndrome, is now considered to be an idiopathic syndrome, is now considered to be an idiopathic inflammatory disease and a regional variant of inflammatory disease and a regional variant of

orbital pseudotumors.orbital pseudotumors.

It is important to exclude the possibility of It is important to exclude the possibility of neoplastic, inflammatory (particularly mycotic neoplastic, inflammatory (particularly mycotic infection such as invasive aspergillosis), and infection such as invasive aspergillosis), and

vasculogenic (e.g. aneurysm) lesions.vasculogenic (e.g. aneurysm) lesions.

Thyroid OphthalmopathyThyroid Ophthalmopathy

Thyroid ophthalmopathy, also called Grave's myositis, occurs Thyroid ophthalmopathy, also called Grave's myositis, occurs most commonly in middle-aged women. This is considered to most commonly in middle-aged women. This is considered to be an autoimmune disorder, involving Extraocular muscles be an autoimmune disorder, involving Extraocular muscles

(EOM) and the Orbital fatty reticulum.(EOM) and the Orbital fatty reticulum.

The involvement may be unilateral or frequently bilateral. EOM The involvement may be unilateral or frequently bilateral. EOM enlargement in thyroid ophthalmopathy and associated enlargement in thyroid ophthalmopathy and associated

compressive neuropathy, if any, can be visualized by CT and compressive neuropathy, if any, can be visualized by CT and MRI. Typically, enlargement involves the muscle belly, sparing its MRI. Typically, enlargement involves the muscle belly, sparing its

tendinous portion .tendinous portion .

Orbital LymphomaOrbital Lymphoma

Lymphomas are solid tumors of the immune system. Lymphomas are solid tumors of the immune system. Most are composed of monoclonal B cells. Most are composed of monoclonal B cells.

Lymphoid tumors account for Lymphoid tumors account for 10%-15%10%-15% of of

orbital masses.orbital masses.

The CT and MRI findings of orbital lymphoma are The CT and MRI findings of orbital lymphoma are non-non-specificspecific and at times can be impossible to differentiate and at times can be impossible to differentiate

from orbital pseudotumors, lacrimal gland tumors, optic from orbital pseudotumors, lacrimal gland tumors, optic nerve tumors, primary orbital tumors, or orbital cellulitis.nerve tumors, primary orbital tumors, or orbital cellulitis.

Lymphomas are more often seen in Lymphomas are more often seen in anterior portionsanterior portions of the orbit, of the orbit, retrobulbar areas,retrobulbar areas, or or the superior orbital the superior orbital

compartment.compartment. Generally the lesions mold Generally the lesions mold themselves to pre-existing structures without themselves to pre-existing structures without

eroding them.eroding them.

Both pseudotumor and lymphoma may have Both pseudotumor and lymphoma may have intermediate or hypointense signal on T1-W.I. intermediate or hypointense signal on T1-W.I. and P.D. MR images, and appear isointense or and P.D. MR images, and appear isointense or hyperintense to fat on T2-weighted MR images, hyperintense to fat on T2-weighted MR images,

with mild to intermediate contrast enhancement.with mild to intermediate contrast enhancement.

Vasculogenic Lesions of the OrbitVasculogenic Lesions of the Orbit Capillary hemangiomas Capillary hemangiomas

are tumors that occur primarily in infants are tumors that occur primarily in infants during the first year of life. The tumor often during the first year of life. The tumor often increases in size for 6-10 months and then increases in size for 6-10 months and then

gradually involutes.gradually involutes.

Most of these lesions are Most of these lesions are extraconal.extraconal. On CT, these On CT, these capillary hemangiomas show an capillary hemangiomas show an intense homogeneous intense homogeneous enhancement.enhancement. MR features of capillary hemangiomas MR features of capillary hemangiomas

are characteristic of long T1 and long T2 lesions. There are characteristic of long T1 and long T2 lesions. There will be marked contrast enhancement .will be marked contrast enhancement .

LymphangiomasLymphangiomas

Lymphangiomas are vascular anomalies and are Lymphangiomas are vascular anomalies and are considered to be venous lymphatic malformations. considered to be venous lymphatic malformations. These lesions present abruptly due to hemorrhage These lesions present abruptly due to hemorrhage

and can also enlarge concomitant with upper and can also enlarge concomitant with upper respiratory infectionsrespiratory infections

Both CT and MRI show the multicompartmental nature Both CT and MRI show the multicompartmental nature of these vascular malformations. At times fluid-fluid of these vascular malformations. At times fluid-fluid

level is present due to bleeding .level is present due to bleeding .

Cavernous HemangiomasCavernous Hemangiomas

Cavernous hemangioma (CH) of the orbit is the Cavernous hemangioma (CH) of the orbit is the most common most common orbital vascular tumor in adults.orbital vascular tumor in adults. The tumor possesses a distinct The tumor possesses a distinct

fibrous pseudocapsule, and therefore, appears as a well-defined fibrous pseudocapsule, and therefore, appears as a well-defined mass. CH may be located anywhere in the orbit but frequently mass. CH may be located anywhere in the orbit but frequently

(83%)(83%) occurs within the occurs within the retrobular muscle cone.retrobular muscle cone. CH appears on CT as a well-defined, CH appears on CT as a well-defined, smoothly marginatedsmoothly marginated, homogeneous, , homogeneous,

rounded, ovoid, or rounded, ovoid, or lobulated soft tissue masslobulated soft tissue mass of increased density with of increased density with variable degrees of contrast enhancementvariable degrees of contrast enhancement

The MRI features include lesion with long T1 and T2 characteristics with mild to moderate or marked enhancement (delayed enhancement)

Cavernous hemangiomas Cavernous hemangiomas should be differentiated fromshould be differentiated from 1-Hemangiopericytoma.1-Hemangiopericytoma.2-Fibrous histiocytoma.2-Fibrous histiocytoma.3-Schwannoma. 3-Schwannoma. 4-Neurofibroma. 4-Neurofibroma. 5-Meningioma.5-Meningioma.6-Rhabdomyosarcoma.6-Rhabdomyosarcoma.7-Orbital varix. 7-Orbital varix. 8-Metastasis8-Metastasis..

Optic Nerve Sheath MeningiomaOptic Nerve Sheath Meningioma

Optic nerve sheath meningioma (ONSM) arises Optic nerve sheath meningioma (ONSM) arises from either the from either the arachnoid cells coveringarachnoid cells covering the the

optic nerve or optic nerve or extensionextension into the orbit from an into the orbit from an intracranial meningioma.intracranial meningioma.

Optic nerve sheath meningioma is Optic nerve sheath meningioma is usually seen in middle-aged women usually seen in middle-aged women

and seen as localized eccentric and seen as localized eccentric expansion, often at the orbital apexexpansion, often at the orbital apex. .

Optic Nerve Sheath MeningiomaOptic Nerve Sheath Meningioma

CT is an informative study to evaluate optic nerve CT is an informative study to evaluate optic nerve sheath meningioma.sheath meningioma.

MRI with contrast to include MRI with contrast to include post-contrast fat post-contrast fat suppressionsuppression pulse sequences is the study of pulse sequences is the study of

choice for the evaluation of optic nerve sheath choice for the evaluation of optic nerve sheath meningioma.meningioma.

Optic nerve Optic nerve sarcoidosissarcoidosis may be confused on CT may be confused on CT and MRI with optic nerve sheath meningioma.and MRI with optic nerve sheath meningioma.

Optic Nerve Glioma Optic Nerve Glioma

Optic nerve glioma (ONG), also called juvenile Optic nerve glioma (ONG), also called juvenile pilocytic astrocytoma, is usually a pilocytic astrocytoma, is usually a tumor of tumor of

childhood (2-8 years).childhood (2-8 years). It can be present at birth and It can be present at birth and is rare in the adult years.Optic nerve glioma in is rare in the adult years.Optic nerve glioma in

children is a children is a benign, well differentiated, and slow-benign, well differentiated, and slow-growing tumor.growing tumor.

Bilateral optic nerve gliomas are characteristic of Bilateral optic nerve gliomas are characteristic of

Type I neurofibromatosis (NF1).Type I neurofibromatosis (NF1).

Optic Nerve Glioma Optic Nerve Glioma contcont

Malignant optic glioma (glioblastoma multiformis) is Malignant optic glioma (glioblastoma multiformis) is primarily seen in adults. Optic nerve glioma is seen primarily seen in adults. Optic nerve glioma is seen

as fusiform enlargement of the optic nerve.as fusiform enlargement of the optic nerve.

Diffuse, tortuous enlargement of the optic nerve Diffuse, tortuous enlargement of the optic nerve with kinking and buckling appearance is a with kinking and buckling appearance is a

characteristic feature of the childhood form of optic characteristic feature of the childhood form of optic nerve glioma and It shows homogeneous or nerve glioma and It shows homogeneous or

heterogeneous enhancement on enhanced CT and heterogeneous enhancement on enhanced CT and MRI scans.MRI scans.

Orbital RhabdomyosarcomaOrbital RhabdomyosarcomaRhabdomyosarcoma is the Rhabdomyosarcoma is the most common orbital malignancy most common orbital malignancy in children.in children. Clinically, its occurrence involves the differential Clinically, its occurrence involves the differential

diagnosis of acute and subacute proptosis of childhood. diagnosis of acute and subacute proptosis of childhood. Rapidly progressing unilateral proptosis is the hallmark of Rapidly progressing unilateral proptosis is the hallmark of

orbital rhabdomyosarcoma. orbital rhabdomyosarcoma. The differential diagnosis of orbital rhabdomyosarcomaThe differential diagnosis of orbital rhabdomyosarcoma

Orbital cellulitis.Orbital cellulitis.Capillary hemangioma.Capillary hemangioma.

Lymphangioma.Lymphangioma.Plexiform neurofibroma.Plexiform neurofibroma.

Teratoma.Teratoma.Dermoid cyst.Dermoid cyst.

Langerhans histiocytosis.Langerhans histiocytosis. Juvenile xanthogranuloma. Juvenile xanthogranuloma.

Leukemic deposit. Leukemic deposit.Metastatic neuroblastoma.Metastatic neuroblastoma.Granulomatous diseases.Granulomatous diseases.

Orbital Rhabdomyosarcoma Orbital Rhabdomyosarcoma cont.cont.

The MRI features of orbital rhabdomyosarcoma are of long The MRI features of orbital rhabdomyosarcoma are of long T1 and T2 lesions. There will be moderate to marked T1 and T2 lesions. There will be moderate to marked

enhancement following IVenhancement following IV. Contrast.. Contrast.

Lacrimal Gland and Fossa Lacrimal Gland and Fossa LesionsLesions

Epithelial tumors (50% benign & 50% malignant) Epithelial tumors (50% benign & 50% malignant) represent about 50% of masses involving the represent about 50% of masses involving the

lacrimal gland. The remaining 50% of lacrimal gland lacrimal gland. The remaining 50% of lacrimal gland masses are the lymphoid-inflammatory type.masses are the lymphoid-inflammatory type.

adenoid cystic (adenocystic) carcinoma.adenoid cystic (adenocystic) carcinoma. mucoepidermoid carcinoma. mucoepidermoid carcinoma.

Adenocarcinoma. Adenocarcinoma. squamous cell carcinoma. squamous cell carcinoma.

undifferentiated (anaplastic) carcinoma. undifferentiated (anaplastic) carcinoma.

Lacrimal Gland and Fossa Lacrimal Gland and Fossa LesionsLesionscont.cont.

Calcification is more common in malignant tumors Calcification is more common in malignant tumors of the lacrimal gland. The MRI features of benign and of the lacrimal gland. The MRI features of benign and malignant epithelial tumors of the lacrimal gland are malignant epithelial tumors of the lacrimal gland are

charactertistic of long T1 and T2 lesions. These charactertistic of long T1 and T2 lesions. These tumors demonstrate moderate to marked tumors demonstrate moderate to marked

enhancement following IV. Contrast.enhancement following IV. Contrast.

Cholesterol crystals and clefts, which are pathognomonic, Cholesterol crystals and clefts, which are pathognomonic, with minor chronic inflammatory infiltratewith minor chronic inflammatory infiltrate..

Orbital traumaOrbital trauma

Intraorbital air

Intraocular haemorrhage

Corneal and lens injury

Rupture of globe

Miscellaneous

Mesenchymal ChondrosarcomaMesenchymal Chondrosarcoma

Cross sectional Cross sectional imaging of globeimaging of globe

Malignant uveal melanomaMalignant uveal melanoma..

Choroidal melanoma, metastasis, hemangioma, Choroidal melanoma, metastasis, hemangioma, lymphoma, granuloma, retinal hemangiomalymphoma, granuloma, retinal hemangioma

THE ENDTHE END

Imaging of Orbit

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